Have you seen this?

[rhoder551]

Great info, everyone! Thanks for your input...

I had a large tomato like that that was very, very good-tasting, this year. The texture was even good. It was just an aesthetic issue in that case. Subsequent tomatoes on the same plant were unaffected, but they tasted about the same. The unaffected ones may have been juicier, however. The plant should have had enough potassium. It wasn't super hot. The plant did experience quite a bit of drought (but that didn't change for subsequent fruits).

I hypothesize that it has a lot to do with the sun (not the amount of total sunlight, but the kind of sunlight, or the composition of it). Sunlight composition seems to change quite a bit from month to month, in my opinion. We really ought to measure that sort of thing (and not be satisfied with the UV index alone). I mean, we could have an index for every visible color of light, and every non-visible type. So, that way, we could tell if there's a lot of green light on any given day, or what-have-you, or how much far infrared is shining.

The composition of colors on the plant itself probably makes a difference, too. It might all look green, but I'm pretty sure there are color variables in there that differ from plant to plant.